1. Field of the Invention
This invention relates to an electromagnetic relay used for opening and closing a circuit by operating an armature according to an excitation of a coil.
2. Description of The Prior Art
Heretofore, there has been used an electromagnetic relay as shown, for example, in FIG. 6 and FIG. 7.
In an electromagnetic relay 100 shown in the figures, a base 101 is fixed with a frame 102 for forming a magnetic circuit, the frame 102 is fixed with an iron core 103a of a coil 103, and fixed contact terminals 106 and 107 provided with respective fixed contacts 104 and 105 are fixed in the base 101 by insert molding.
A conductive hinge 108 having stiffness is engaged to a projection 102b provided on an upper face 102a of the frame 102 in FIG. 6 at one end thereof and is attached to an armature 109 at another end thereof, the armature 109 is so designed as to rotate around the projection 102b provided on the frame 102 within a range restricted by contacting a restraint part 108a of the hinge 108 with the frame 102.
A coil spring 110 is engaged between a hook 109a provided to the upper end of the armature 109 and a hook 102d provided to the upper end of a side wall 102c of the frame 102 on the right side in FIG. 6.
And, two movable pieces 113 and 114 which are disposed with movable contacts 111 and 112 respectively at lower ends thereof in FIG. 6 are fixed to the armature 109 through a block 109a made of non-conducting material so as to be insulated from the armature 109 and to be united with the armature 109.
The movable contact pieces 113 and 114 are connected to ends of woven wires 115 and 116 at upper ends thereof by spot welding respectively as shown in FIG. 6, and the other ends of the respective woven wires 115 and 116 are connected similarly by spot welding to respective movable contact terminals 117 and 118 which are fixed opposite to the fixed contacts 104 and 105 in the base 101 by insert molding.
Furthermore, either end of a wound wire 103b of the coil 103 is connected to respective coil terminals 119 and 120 fixed similarly in the base 101.
The electromagnetic relay 100 is so structured as to be assembled into the state in which the armature 109 is detached from the iron core 103a by fixing the frame 102 to the base 101 with a screw (not shown) while contacting the respective movable contact pieces 113 and 114 with the respective movable contact terminals 117 and 118 at the state in which the armature 109 is connected to the frame 102 by the hinge 108 and the coil spring 110.
At the unexcited state of the coil 103 shown in FIG. 6, the armature 109 is energized in the clockwise direction around the one end of the hinge 108 by tensile force of the coil spring 110, and the respective movable contact pieces 113 and 114 are in contact with the respective movable contact terminals 117 and 118.
In this state, supplying a predetermined electric current to the coil 103 through the coil terminals 119 and 120 by changing a switch (not shown), magnetic flux passing from the iron core 103a to the armature 109 through the frame 102 and the hinge 108 is generated by the excitation of the coil 103, and the armature 109 is attracted toward the iron core 103a, that is in the anticlockwise direction in FIG. 6.
Thereby, the respective movable contact pieces 113 and 114 separate from the movable contact terminals 117 and 118 and the movable contacts 111 and 112 disposed on the movable contact pieces 113 and 114 come in contact with the respective fixed contacts 104 and 105, so that the movable contact terminals 117 and 118 are connected electrically with the fixed contact terminals 106 and 107, respectively.
And in this state, cutting the power supply through the coil terminals 119 and 120 by changing the switch, the coil 103 becomes unexcited state and the armature 109 returns in the clockwise direction in FIG. 6 by the tensile force of the coil spring 110, so that the respective movable contacts 111 and 112 separate from the respective fixed contacts 104 and 105, and the movable contact pieces 113 and 114 come in contact with the movable contact terminals 117 and 118. Thereby, the electromagnetic relay 100 returns to the state as shown in FIG. 6.
However, aforementioned conventional electromagnetic relay 100 is so structured as to energize the armature 109 through the hinge 108 in the direction away from the iron core 103a by the coil spring 110 engaged between the armature 109 and the frame 102, and the respective movable contact pieces 113 and 114 are connected with the respective movable contact terminals 117 and 118 through the woven wires 115 and 116. Accordingly, there is a problem in that it is unfavorable in the cost since the number of parts is too numerous.
Furthermore, it is not possible to keep the distance between the armature 109 and the iron core 103a constant owing to dimensional errors of the respective parts such as the movable contact pieces 113 and 114, the coil spring 110, the hinge 108 and the frame 102. There is another problem since some differences in the performance of the relay may arise among products.